Some wireless products are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards (WiFi), whereas others use a cellular network. There have been many activities in the cellular-Wi-Fi integration area in the past few years. Cellular (e.g., Long Term Evolution [LTE]/3G) and WiFi networks can be integrated via a loose coupling or a tighter coupling. Some work has offered mechanisms that consider a loose coupling of LTE and WiFi networks. Proxy MIPv6 is an example in which a loose coupling of LTE and Wi-Fi networks is considered. There is an interest to move towards a tighter coupling network architectures, as these architectures can provide a more seamless mobility experience to users. For example, some companies have proposed to include tighter coupling of LTE-WiFi networks for 3GPP Release 12.
There are many constraints in supporting dual mode LTE-WiFi User Equipment (UE) (e.g., a handset). One constraint is that the cost of the handset goes up: for example, supporting two RF chips increases the cost of device. There are also interference issues that need to be tackled when LTE as well as WiFi RF are active on the same device, especially if they are on similar RF frequencies (e.g., 2.4 GHz/2.3 GHz). There are also battery issues when two RF chains are active simultaneously, and one is communicating data over two radio access technologies. There are devices that support two RF chips (one for cellular and one for Wi-Fi), but only one is active at a time due to these issues. On the other end, there are more expensive devices that support two active RF chips, but that support is typically for select spectrum bands only.